1. Field of the Invention
The present invention relates to a burn-in system for conducting a burn-in test for extracting initial defects of semiconductor integrated circuits and other various types of electronic devices, more particularly relates to a burn-in system for simultaneously conducting a burn-in test on a large number of electronic devices. In countries where incorporation by reference of other documents is allowed, the content described in the following application is incorporated into the present application by reference and made part of the description of this application.
Japanese Patent Application No. 2004-079623, filed on Mar. 19, 2004
2. Description of the Related Art
As a burn-in system used for burn-in tests—a type of screening test for extracting initial defects of electronic devices and removing initially malfunctioning devices, there is known a system holding a burn-in board mounting a large number of devices under test in a burn-in chamber, applying a predetermined voltage to impart electrical stress, and heating the air in this burn-in chamber to impart a predetermined temperature of thermal stress or a system not heating the air in the burn-in chamber, but instead providing heater blocks and bringing the heater blocks into direct contact with the devices under test to impart thermal stress for a burn-in test.
In such a burn-in system, since a burn-in test is conducted over a long period of time from several hours to several tens of hours, the test efficiency is raised by conducting the burn-in test simultaneously for a large number of electronic devices. At this time, the test is desirably performed in a state giving as uniform a thermal stress as possible to the large number of devices under test.
However, in actuality, even with the same lot of electronic devices, inherent defects, manufacturing variations, etc. result in each electronic device differing in consumed power, so the electronic devices sometimes vary in amounts of self generated heat as well. Therefore, even if simply heating the air in the burn-in chamber or bringing heater blocks into contact with the devices, it is sometimes difficult to apply a uniform thermal stress to the simultaneously tested plurality of electronic devices.
In particular, recent IC chips have become larger in capacity, higher in performance, and faster in speed. Along with this, the amount of self generated heat has been increasing as a general trend. Along with this, the variation in amount of self generated heat has also become larger as a general trend. Therefore, accurate control of the temperature of each electronic device in a burn-in test is being demanded.